Patients and methods

Radiation treatment planning was performed with a hybrid and a 3D-CRT treatment plan for 20 patients. Hybrid plans were implemented with two tangential IMRT fields and a VMAT field in the angular range of the tangents. Verification of the plan was performed with a manufacturer-independent measurement system consisting of a detector array and rotation unit.

Results

The mean values of the heart dose for the entire patient collective were 3.6 ± 2.5 Gy for 3D-CRT and 2.9 ± 2.1 Gy for the hybrid technique (p < 0.01). For the left side (n = 10), the mean values for the left anterior descending artery were 21.8 ± 7.4 Gy for 3D-CRT and 17.6 ± 7.4 Gy for the hybrid technique (p < 0.01). The mean values of the ipsilateral lung were 11.9 ± 1.6 Gy for 3D-CRT and 10.5 ± 1.3 Gy for the hybrid technique (p < 0.01). Calculated dose distributions in the hybrid arm were in good accordance with measured dose (on average 95.6 ± 0.5 % for γ < 1 and 3 %/3 mm). The difference of the mean treatment time per fraction was 7 s in favor of 3D-CRT.

Conclusion

Compared with the established 3D-CRT technique, the hybrid technique allows for a decrease in dose, particularly of the mean heart and lung dose with comparable target volume acquisition and without disadvantageous low-dose load of contralateral structures. Uncomplicated implementation of the hybrid technique was demonstrated in this context. The hybrid technique combines the advantages of tangential IMRT with the superior sparing of organs at risk by VMAT.

Schlüsselwörter

Notes

Acknowledgments

Author contributions: V. Jöst and M. Kretschmer contributed equally in developing the study design, collecting data, analyzing and interpreting the data, statistical analysis, and drafting the manuscript. M. Sabatino contributed to developing the study design and revising the manuscript. F. Würschmidt performed the PTV delineations and revised the manuscript. J. Dahle performed the PTV delineations and revised the manuscript. F. Ueberle revised the manuscript. J. Lorenzen performed the delineation of coronary arteries and revised the manuscript. All authors read and approved the final manuscript.

Compliance with ethical guidelines

Conflict of interest

V. Jöst, M. Kretschmer, M. Sabatino, F. Würschmidt, J. Dahle, F. Ueberle, and J. Lorenzen state that there are no conflicts of interest.